WASHINGTON, Sept 13 (Reuters) - U.S. President Donald Trump was set to host Democratic and Republican House lawmakers at the White House on Wednesday, seeking to build support across the political spectrum for tax reform that he said should include tax cuts for the middle class.

The Republican president, who has shown a new willingness to engage with Democrats in recent days, discussed tax plans over dinner on Tuesday with a small group of Republican and Democratic senators as he tries to push for rapid tax legislation.

Several senators who attended the dinner said in television interviews on Wednesday that Trump had been clear the tax package could not be focused on wealthy Americans.

WASHINGTON, DC - SEPTEMBER 06: (EDITORS NOTE: Retransmission with alternate crop.) U.S. Senate Minority Leader Sen. Chuck Schumer (D-NY) (L) makes a point to President Donald Trump (2nd L) in the Oval Office as White House Director of Legislative Affairs Marc Short (R) looks on towards the end of a meeting between the President and Congressional leaders prior to President Trump's departure from the White House for a tax reform event in North Dakota September 6, 2017 in Washington, DC. President Trump has struck a deal at the meeting with Sen. Schumer and House Minority Leader Rep. Nancy Pelosi (D-CA) to fund the disaster relief for Hurricane Harvey, raise the debt ceiling for three months and keep the government open through the end of December. (Photo by Alex Wong/Getty Images)

Republicans control both chambers of Congress and the party's leaders have been trying for most of the year to come up with a detailed tax plan while ignoring the Democrats. Democrats have criticized their effort as aimed mostly at the rich.

"The president stressed that he wants this to be a middle class tax cut," Republican Pat Toomey, one of the senators who attended the Tuesday dinner, told MSNBC.

Democratic Senator Joe Manchin told CBS News that Trump "was adamant this is not a tax cut for the rich" and that the White House was "very aggressive" on the need for a bipartisan plan.

The White House called the dinner "highly productive," saying in a statement it would "spur constructive discussion."

Trump is promoting his goals of a simpler U.S. tax code with lower rates, including on corporate taxes, even as a detailed plan has yet to emerge from either the White House or Congress.

He was due to meet on Wednesday with 13 lawmakers from the House of Representatives, including eight Democrats and five Republicans. House Republican leaders were also expected to give their members an update on the tax reform effort, including a general timeline to pass a bill.

"The approval process for the biggest Tax Cut & Tax Reform package in the history of our country will soon begin. Move fast Congress!" Trump wrote.

Trump reached a surprising deal last week with Democratic leaders on fiscal issues, blindsiding Republican leaders. That led to a bill that Trump signed on Friday extending the government debt limit for three months and providing about $15 billion in hurricane-related aid. (Reporting by Susan Heavey, Roberta Rampton, David Morgan and Makini Brice; Editing by Frances Kerry)